Multi-compartment bags are known for use in a variety of applications, including mixing two reactants to produce an endothermic or exothermic reaction for a number of uses, including therapy for muscular injury or circulatory problems or heating or cooling food. Multi-compartment bags have also been used for applications such as mixing resins with an initiator prior to use of the resin.
Cold packs have been used to treat injuries such as sprained muscles or injured joints. Generally, the cold packs are used to slow blood flow, and reduce swelling, pain and further damage.
Heat packs have been used to warm muscles or reduce cramping. Generally, heat packs increase blood flow.
Hot and cold packs are generally of two types: those that require external heating or cooling, and "chemical packs" which mix two or more reactants to cause an endothermic or exothermic reaction. It is desired that chemical packs have a long shelf life and be activated only upon an intentional activation, and not in shipping or handling.
The chemical packs generally come in two varieties: the bag-in-bag type or the side-by-side type. The bag-in-bag type pack has two separate bags, with a smaller bag containing one of the reactants included within the larger bag which contains the other reactant. Bag-in-bag chemical packs suffer from the significant disadvantage that there is a large surface area, represented by the exterior surface of the smaller bag, between the first reactant and the second reactant. Here, if a reactant is a liquid or gas, it will migrate through the plastic material of the smaller bag and into the second reactant causing a pre-activation intermixing of the reactants which results in a short shelf life and a lower efficiency upon intentional activation. This migration through the smaller bag can be slowed by using a thicker plastic material for the smaller bag; however, when a thicker smaller bag is utilized, it becomes more difficult to activate the pack when activation is desired. Also, with the bag-in-bag design, it is sometimes difficult to rupture the smaller bag. A number of prior art devices have utilized a rigid spike to facilitate rupturing the smaller bag. This presents significant shortcomings in that the rigid spike may puncture the larger bag in use or in shipping and handling causing external leaking.
The side-by-side bags utilize a breakable seal between two compartments located side-by-side, each compartment containing one of the reactants. These side-by-side packs attempt to utilize a strong seal around the perimeter of the bag and a weak seal to separate the two compartments. This is very difficult to do on a consistent basis and with known manufacturing techniques and leads to a situation where a force, intended to mix the two reactants, breaks an exterior seal causing a leak of the reactants onto the potential user.
Various mechanical devices have been used to prevent the mixing of two components in multi-compartment bags. These mechanical devices may be either externally mounted or internal to the bag, such as, for example, a groove provided on the inner side of one sheet which connects with a rib on the inner side of the opposite sheet, the groove and rib being engaged to seal and prevent intermixing of the two reactants, with the rib and groove being separated to permit intermixing. These mechanical seals suffer from significant shortcomings. First, mechanical seals invariably leak and are not as reliable as other sealing methods. Also, during shipping and handling, mechanical seals have a higher rate of accidental activation, resulting in unusable product.
U.S. Pat. No. 4,427,010 to Marx utilizes a side-by-side bag wherein a breakable wall is used instead of a breakable seal. This overcomes the problem of manufacturing a seal which ruptures at the desired force; however, this bag still has the significant shortcoming of a large surface area between the first and second reactants which, upon migration of one reactant through the plastic sheet into the other reactant, reduces the shelf life and efficiency of the product.
Another shortcoming of the prior art chemical packs is that they do not provide any means to fasten the chemical pack to a user wishing to apply the chemical pack in a therapeutic fashion to a particular part of his body. Prior art ice packs, i.e., packs wherein ice is added for each use, have employed ties and other fastening means. However, these ice pack fastening means suffer from several shortcomings. First, if not used carefully or if overstressed, these fastening means may cause the rupturing of a seam or tearing of a pack resulting in external leaking of ice and water. While this is an undesired result with ice packs, it presents a much more serious concern with chemical packs, where the rupturing of a seal or tearing of a pack could result in release of chemicals onto the user. Also, depending upon the ice pack chosen, the ties may be difficult to use or expensive to manufacture.
There exists a need for a multi-compartment bag for mixing two substances, and more particularly, for a hot or cold chemical pack for mixing two substances, which has a long shelf life and wherein the force required to mix the two substances is predictable, such that the substances will be mixed upon an intended activation by the user, and not in normal handling and shipping. There further exists a need for a chemical pack with suitable ties for fastening the chemical pack to a user.